1. Field of the Invention
The invention relates to a hydraulic fluid pump of a vehicle brake system, having a delivery mechanism for delivering hydraulic fluid counter to a hydraulic counterpressure existing in a portion of the vehicle brake system. The invention also relates to a vehicle brake system having a hydraulic fluid pump of this kind.
2. Description of the Prior Art
Hydraulic fluid pumps of vehicle brake systems are known in which for delivering hydraulic fluid or brake fluid to the vehicle brake system, and particularly for returning the brake fluid from the vehicle brakes and/or for actively building up brake pressure, a plurality of reciprocating piston pumps are used as delivery mechanism. These reciprocating piston pumps are also called pump elements.
As a rule, the pump elements are driven via an electric motor, with an eccentric element seated on a drive shaft. Alternatively, cam drives or similar mechanisms are possible as well. Depending on the eccentricity of the eccentric element and on the diameter of the piston used in the pump element or reciprocating piston pump, the result is a constant delivery volume per revolution of the electric motor.
On the assumption of a complete filling of the pressure chamber at the pump element or the reciprocating piston pump, and ignoring the efficiencies, the result in all operating ranges of the hydraulic fluid pump is a linear relationship between the hydraulic load torque (pressure p) and electrical output (current intensity I, when the voltage U is constant). Because of this linear relationship, even though the hydraulic load torque in known hydraulic fluid pumps can be well set by means of simple regulation of the electric current intensity, such hydraulic fluid pumps do not operate optimally in all parts of the operating range.